This invention relates to a method and an apparatus for detaching fiber tufts from textile fiber bales formed of cotton, chemical fibers or the like. The apparatus has a detaching device which travels back-and-forth above the fiber bales and which may be lowered thereonto. The detaching device removes fiber tufts from the upper surface of the fiber bales and advances the fiber tufts to a tuft transporting device. The bale height is divided into at least three detaching zones.
The fiber bales are delivered to the spinning preparation plant in a compressed state. After removing the constraining ties, such as straps, wire or the like, the bales, by virtue of their natural resiliency, expand in a vertical direction. Consequently, the bales from which fiber tufts are to be removed do not have a uniform density as viewed in the vertical direction. The fiber bales have the greatest density in a mid zone. As a result of such an uneven density distribution, upon detaching fiber tufts from an originally upper bale zone lying above the mid zone and later, from an originally lower bale zone lying below the mid zone, less fiber tufts (by weight) are detached and delivered than during the fiber tuft detachment from the mid zone of the bale. This means that during a starting period and during a terminal period of the detaching operation performed on a bale series, the downstream-connected machines are supplied with less fiber material (measured in weight) per time unit than during the detaching period when fiber tufts are removed from the mid zone of the bales.
In accordance with a known process, the adaptation of the weight of the fiber tuft quantities (production quantities) delivered by the detaching device per time unit to the different bale densities is achieved by varying the vertical feed of the detaching device for consecutive passes. In such a method the depth of detaching operation in the upper bale zone in which the density of the fiber material increases downwardly, is gradually decreased from a predetermined maximum detaching depth down to a detaching depth determined for the mid zone. The upper bale zone is delimited by a predetermined number of passes of the detaching device. In the mid zone where the bale density is the greatest, the predetermined detaching depth is maintained constant to thus delimit such mid zone. In accordance with a further known process, in the lower bale zone (decreasing density in the vertical direction) additionally the detaching depth is gradually increased; the maximum detaching depth and the number of passes of the detaching device are predetermined. In case, however, the output quantities have to be rapidly altered and the vertical feed is altered during one or several passes, the difficulty is encountered that the upper surface of the bales will be wavy which is an undesirable phenomenon. It is a further disadvantage of the known process that the fiber tuft dimensions fluctuate when the detaching depth is altered.